Diversity of endophytic bacterial populations associated with Cd-hyperaccumulator plant Solanum nigrum L. grown in mine tailings

Abstract

Despite the broad application of molecular approaches for the analysis of bacterial communities in a wide range of natural habitats, little information is available on the diversity of bacterial endophytes in the hyperaccumulators growing in heavy-metal contaminated sites. In this study, the diversity of bacterial endophytes associated with Cd-hyperaccumulator Solanum nigrum L. growing in mine tailing was analyzed by 16S rDNA clone library technique. In total, 197 individual sequences comprising 40 different Operational Taxonomic Units (OTUs) were used to assess the diversity of bacterial endophytes. Phylogenetic analysis revealed that the majority of clones were affiliated with Proteobacteria (61.93%; 19 OTUs), which included α (41.12%; 11 OTUs), β (6.09%; 4 OTUs) and γ (14.72%; 4 OTUs) subclasses. Other clones belonged to Bacteroidetes (12.18%; 5 OTUs), Firmicutes (2.03%; 2 OTUs), Actinobacteria (18.78%; 10 OTUs) and uncultured bacteria (5.08%; 4 OTUs). The dominant genera were Sphingomonas and Pseudomonas, which accounted for 24.37% and 12.18% of total clones respectively. These findings suggested that the diversity of endophytic bacterial populations was abundant in S. nigrum L., and these bacterial endophytes should be targeted for future research to determine their functional role, if any, in heavy metal stress reduction.